1. Field of the Invention
Orthopedic structures find wide use in the immobilization of limbs in aiding the healing process. In the maintenance of fixation of fractured bones, immobilization of inflamed or injured joints, in cases of disease or trauma and for the support and immobilization of ligamentous and muscular structures in instances of sprains and strains, it is necessary to encase the limb in a partially or completely surrounding rigid form or cast. The immobilized limb may be encased in such rigid structure for long periods of time, frequently as much as 6 weeks or more.
There are two major considerations for a cast. The first consideration concerns the formation of the cast. A satisfactory cast material should be easily handleable, should not have properties which deleteriously affect the limb, particularly the skin, should have a reasonable setting time or work life, so as to allow a reasonable period of time in which to mold the cast material about the limb, should be flexible during application to the limb so as to readily assume the shape of the limb, should be free of offensive or noxious solvents or other chemicals, and should set within a relatively short time under relatively mild conditions. In addition, it is desirable that a minimum of equipment should be involved in formation of the cast. Also it is desirable that during the forming of the cast the material does not generate an uncomfortable exothermic reaction, and that upon drying, curing or setting up it has a negligible shrinkage factor.
The second consideration concerns the properties of the cast after it is formed. Desirably, the cast should be of a light weight material so as to minimize the inconvenience to the wearer, porous so as to allow the underlying skin to breathe and not become macerated or otherwise irritated, should have sufficient structural strength so as to retain its structure under normal usage, should be sufficiently sturdy to maintain the joint or limb in the immobilized position and protect the joint or limb from jars, and should be easily removable. An optimum cast should also be water-proof, (i.e., the impregnated fabric material itself should not absorb and retain water), be as x-ray transparent as possible, be highly impact and abrassion resistant, and should exhibit a versatility to be reformed, and repaired after the initial cast is formed in place.
Because of the numerous and varied requirements for an orthopedic cast material, none of the presently known immediately available cast materials provide all or substantially all of the properties indicated above.
2. Description of the Prior Art
U.S. Pat. No. 3,692,023 describes the use of polycaprolactone as a cast material employing permeable or porous base webs impregnated with a polymer. See also U.S. Pat. Nos. 3,592,190, 2,301,426, 2,616,418, 3,420,231, 3,490,444, 3,592,190, 3,604,413.